Agriculture Department scientists raised rice in controlled lab environments. They grew some in CO2 levels reflecting atmospheric concentrations from a century ago — through to what’s expected to exist in coming decades. And with each stepwise rise in CO2, the weedy rice increasingly hybridized with the crop plants, reinserting wild genes that breeders had spent great effort to remove or modify.
The result was a diminishing of the value and quality of the cultivated rice — essentially transforming it into a weed, explains Lewis Ziska of the USDA Agricultural Research Service in Beltsville, Md. “That’s sort of the science fiction aspect of this,” he says. Likening it to Invasion of the Body Snatchers, “Whatever [seed] the good plant produces is now going to be bad seed.”
In addition, hybrids in the new tests retained the crop plant’s genetic immunity to a weed killer. Indeed, Ziska says, the latter feature may partially explain the diminishing value of herbicide treatments on rice in recent years.